It is assumed that the main source of marine litter is terrestrial from rivers and waterways. Therefore, the dominant marine litter pathways from land sources to the ocean is via coastal regions. In coastal zones, debris can accumulate, return to the emerging beach, sink to the seafloor, or migrate to the open sea where it can converge in oceanic accumulation regions such as subtropical gyres. Near the shoreline, coastal transport processes are crucial in determining marine debris’ residence times and accumulation zones. However, the transport mechanisms of floating marine debris in coastal zones remain poorly understood, primarily due to the complex geometry and influence of coastal processes which pose difficulties in incorporating them into Lagrangian numerical models at coastal scales. Moreover, coastal regions are highly susceptible to the impacts of the presence of marine litter affecting ecological resources, social activities and economic assets. This work presents an integrated approach to marine litter pollution in coastal regions using developed coastal numerical models and scientific monitoring using a citizen science approach. The methodology is presented for the Barcelona coastline region.

Pteropods are a group of cosmopolitan holoplanktic gastropods that produce an aragonite shell and play an important role in both marine ecosystems and geochemical cycles. In addition to being affected by anthropogenic impacts that include warming and changes in carbonate system parameters, the Mediterranean Sea is considered to be understudied concerning pteropods dynamics and abundances. This work aims to document the modern spatial and temporal distributions of pteropods populations in the Northwestern and Central Mediterranean Sea (Gulf of Lions and Strait of Sicily), respectively. We present data from two sediment-trap records that cover the timeframe between early 1996 and early 2004 for the Gulf of Lions and late 2013 to late 2014 for the Sicily Strait. A total of 843 pteropod shells and 18 different species were identified. Limacina inflata, Creseis virgula and Creseis clava were the most abundant species in the Gulf of Lions, while in the Sicily Strait, C. conica replaced C. clava as the most abundant species. These taxons represented around 70% of the total individuals identified in both sites. Overall, our results suggest a greater pteropod abundance in the Gulf of Lions than in the Sicily Strait, most likely due to enhanced food conditions. In the Gulf of Lions, maximum fluxes occurred in autumn (32.5% of the annual pteropod fluxes registered in October), while in the Sicily Strait peak fluxes occurred in winter (30.5% of the annual pteropod fluxes registered in January). Comparison of temporal changes pteropod fluxes with satellite sea surface temperature (SST), and chlorophyll-a concentration suggest a possible positive effect of high algal accumulation and cool water conditions in the Strait of Sicily on the main pteropod groups. In turn, no clear relationships between pteropod groups, SST and chlorophyll-a were identified in the Gulf of Lions, highlighting the effect of salinity and carbonate system parameters. Overall, and despite the limitations associated with the use of sediment traps for pteropod population monitoring, the consistency of our results with the literature supports the use of sediment traps as useful tools for documenting the diversity and temporal distribution of pteropods.

The Sicily Channel, located in the central Mediterranean Sea, represents a key point for the regional oceanographic circulation, as it is regarded as the sill that separates the western and eastern basins. Therefore, it is regarded as a unique zone in the well-documented west-to-east Mediterranean productivity gradient. Here we present a time series of settling planktonic foraminifera assemblages from November 2013 to October 2014. Altogether, 19 samples from the sediment trap C01 deployed at a water depth of around 400 m have been used. More than 3700 individuals and 15 different species have been identified. Globorotalia inflata, Globorotalia truncatulinoides, Globigerina bulloides, Globigerinoides ruber, and Globigerinoides ruber (pink) were the five main species identified, accounting for more than 85 % of the total foraminifera. The total planktonic foraminifera flux mean value was 630 shells m−2 d−1, with a minimum value of 45 shells m−2 d−1 displayed during late autumn 2013 and a maximum of 1890 shells m−2 d−1 reached during spring 2014. This is likely due to the regional oceanographic configuration and the marked seasonality in the surface circulation. During spring and winter, Atlantic Water (AW) dominates the surface circulation, bringing cool and nutrient-enriched waters. This results in a planktonic foraminifera flux increase and a dominance of western basin taxa. During summer and autumn, the circulation is dominated by the eastern warm and oligotrophic Levantine water, which leads to a planktonic foraminifera flux decrease and the dominance of eastern basin species. Our comparison with satellite-derived sea surface temperatures (SSTs) and chlorophyll a data showed that G. inflata was associated with cool and nutrient-rich conditions, while both G. ruber morphotypes were associated with warm and oligotrophic conditions. However, no trends were identified for G. truncatulinoides or G. bulloides. As the latter species flux increased coincidently with that of benthic foraminifera, we considered that this species might have a resuspended origin. The comparison of the Sicily Channel data with other Mediterranean time series indicates that the annualized planktonic foraminifera flux was lower than in the westernmost Alboran Sea but higher than in the easternmost Levantine Basin. The Sicily Channel species diversity was the highest among the compared zones, highlighting the influence of the different basins and its transitional aspect from a planktonic foraminifera population perspective. Finally, we compared the settling planktonic foraminifera assemblage with the assemblages from seabed sediment located in the vicinity of the Sicily Channel. The differences in the seabed populations varied according to the sites studied. The deep-dwelling species dominated the settling assemblage samples, while eutrophic and oligotrophic species were more abundant in the sediment. Finally, a high-resolution chronology comparison allowed us to show that this planktonic foraminifera population shift likely developed during the late Holocene prior to the industrial period; however, its causes remain uncertain.

Plastic pollution is widely recognized as one of the major threats to marine ecosystems. However, our knowledge on the ecological interactions between plastic and marine fauna is still limited. Here, we analyzed the substrate preferences for oviposition in the small-spotted catshark (Scyliorhinus canicula) and explored the influence of pollution, environmental conditions, and fishing pressure as potential drivers. For the first time, we report this catshark species using marine debris for oviposition, unraveling a behavioral shift in the oviposition substrate preferences towards plastics, particularly ghost fishing gear, when biological substrates are unavailable. Our results indicate that this behavioral change may be driven by the combined effects of plastic pollution and habitat degradation. Preferences also change with depth, with a larger preference for the hydrozoan Lytocarpia myriophyllum on the continental shelf, followed by sponges, as in this region mesophotic and deep benthic communities are still more abundant although impacted by human pressures. In contrast, on the continental slope, the preference shifts to tube-dwelling polychaetes and plastics, primarily ghost fishing gear, due to the limited availability of biological substrates in this region. We highlight that plastic-fish interactions may become increasingly recurrent as plastic substrates increase and habitat forming invertebrates decline due to trawl fishing and other anthropogenic activities, especially in the Mediterranean Sea. The implications of this behavior for catshark fitness are still largely unknown, which prompts further research concerning the potential impact on its survival and/or dispersal in the plastic age and highlights the urgency of preserving biogenic habitats.

The wide continental shelf of the Gulf of Lion in the NW Mediterranean is a region subject to pronounced atmospheric and oceanic interactions. Persistent cold northerly winds trigger progressive cooling of shelf waters, instigating a notable increase in seawater density. This dense water is forced to overflow by the slope, primarily channeled through the submarine canyons and especially through the southernmost Cap de Creus submarine canyon. Known as dense shelf water cascading, this intricate phenomenon exerts a pivotal influence not only on regional oceanographic dynamics but also on seafloor morphology and deep-sea living resources, warranting comprehensive investigation.To understand the interannual variability of cascading events spanning recent decades, we use the Med MFC physical reanalysis dataset, which encompasses the Mediterranean Sea. This dataset has proven invaluable, exhibiting robust correlations with in-situ observations of dense shelf water cascading via moored instrumentation, thereby offering unprecedented insights into the spatiotemporal evolution of water properties and dynamics within the Gulf of Lion.Our study quantifies the influence of the shelf water density modulation by the buoyancy fluxes in the air-sea interface. Leveraging data from atmospheric ERA5 and hydrological GloFAS reanalyses, we unveil a comprehensive understanding of the ocean-atmosphere interaction dynamics within this region. Specifically, we analyze the interannual variability in the buoyancy fluxes calculated from the main forcing agents impacting shelf water density: river freshwater input, wind speed, air-sea temperature contrast, absolute humidity, and precipitation.Our analysis reveals a significant correlation between these fluxes and the East Atlantic pattern (EA), which is one of the main modes of climate variability in the atmosphere. This underscores the intricate interplay between oceanic processes and broader atmospheric dynamics, particularly over the Gulf of Lion. Our findings offer insights into the mechanisms governing dense shelf water cascading and natural variability, thus augmenting our understanding of regional climate dynamics and enhancing predictive capabilities, and help foresee its occurrence and evolution in the context of climate change.

Artificial turf (AT) is a surfacing material that simulates natural grass by using synthetic, mainly plastic, fibers in different shapes, sizes and properties. AT has spread beyond sports facilities and today shapes many urban landscapes, from private lawns to rooftops and public venues. Despite concerns regarding the impacts of AT, little is known about the release of AT fibers into natural environment. Here, for the first time, we specifically investigate the presence of AT fibers in river and ocean waters as major conduits and final destination of plastic debris transported by water runoff. Our sampling survey showed that, AT fibers - composed mainly of poly-ethylene and polypropylene - can constitute over 15% of the mesoplastics and macroplastics content, suggesting that AT fibers may contribute significantly to plastic pollution. Up to 20,000 fibers a day flowed down through the river, and up to 213,200 fibers per km2 were found floating on the sea surface of nearshore areas. AT, apart from impacting on urban biodiversity, urban runoff, heat island formation, and hazardous chemical leaching, is a major source of plastic pollution to natural aquatic environments.

Increasing amount of anthropogenic litter in the marine environment has provided an enormous number of substrates for a wide range of marine organisms, thus serving as a potential vector for the transport of fouling organisms. Here, we examined the fouling organisms on different types of stranded litter (plastic, glass, rubber, foam sponge, cloth, metal and wood) on eight beaches along the southeast coast of India. In total, 17 encrusting species belonging to seven phyla (Arthropoda, Bryozoa, Mollusca, Annelida, Cnidaria, Chlorophyta and Foraminifera) were identified on 367 items, with one invasive species, the mussel Mytella strigata, detected. The most common species associated with marine litter were the cosmopolitan bryozoans Jellyella tuberculata (%O = 31.64 %) and J. eburnea (28.61 %), the barnacle species Lepas anserifera (29.97 %), Amphibalanus amphitrite (22.34 %) and Amphibalanus sp. (14.16 %), and the oyster species Saccostrea cucullata (13.62 %) and Magallana bilineata (5.44 %). We also reported the first records on stranded litter of four species: the gastropod species Pirenella cingulata and Umbonium vestiarium, the foraminiferan Ammonia beccarii, and the oyster M. bilineata. This study is thus the first documentation of marine litter as a vector for species dispersal in India, where the production and consumption of plastic rank among the highest in the world. We also highlight the increasing risk of invasions by non-indigenous organisms attached to debris along the southeast coast of India. Comprehensive monitoring efforts are thus needed to elucidate the type of vectors responsible for the arrival of invasive species in this region. Raising awareness and promoting education are vital components in fostering sustainable solutions to combat plastic pollution in the country and globally.

Plastics have been proposed as vectors of bacteria as they act as a substrate for biofilms. In this study, we evaluated the abundance of faecal and marine bacteria and antibiotic resistance genes (ARGs) from biofilms adhered to marine plastics. Floating plastics and plastics from sediments were collected in coastal areas impacted by human faecal pollution in the northwestern Mediterranean Sea. Culture and/or molecular methods were used to quantify faecal indicators (E. coli, Enterococci and crAssphage), and the ARGs sulI, tetW and bla(TEM) and the 16S rRNA were detected by qPCR assays. Pseudomonas and Vibrio species and heterotrophic marine bacteria were also analysed via culture-based methods. Results showed that, plastic particles covered by bacterial biofilms, primarily consisted of marine bacteria including Vibrio spp. Some floating plastics had a low concentration of viable E. coli and Enterococci (42% and 67% of the plastics respectively). Considering the median area of the plastics, we detected an average of 68 cfu E. coli per item, while a higher concentration of E. coli was detected on individual plastic items, when compared with 100 ml of the surrounding water. Using qPCR, we quantified higher values of faecal indicators which included inactive and dead microorganisms, detecting up to 2.6 x 10(2) gc mm(-2). The ARGs were detected in 67-88% of the floating plastics and in 29-57% of the sediment plastics with a concentration of up to 6.7 x 10(2) gc mm(-2). Furthermore, enrichment of these genes was observed in biofilms compared with the surrounding water. These results show that floating plastics act as a conduit for both the attachment and transport of faecal microorganisms. In contrast, low presence of faecal indicators was detected in plastic from seafloor sediments. Therefore, although in low concentrations, faecal bacteria, and potential pathogens, were identified in marine plastics, further suggesting plastics act as a reservoir of pathogens and ARGs.

The dumping of an estimated amount of 57 million tons of hazardous sulfide mine waste from 1957 to 1990 into Portmán's Bay (SE Spain) caused one of the most severe cases of persistent anthropogenic impact in Europe's costal and marine environments. The resulting mine tailings deposit completely infilled Portmán's Bay and extended seawards on the continental shelf, bearing high levels of metals and As. The present work, where Synchrotron XAS, XRF core scanner and other data are combined, reveals the simultaneous presence of arsenopyrite (FeAsS), scorodite (FeAsO₄·2H₂O), orpiment (As2S3) and realgar (AsS) in the submarine extension of the mine tailings deposit. In addition to arsenopyrite weathering and scorodite formation, the, the presence of realgar and orpiment is discussed, considering both potential sourcing from the exploited ores and in situ precipitation from a combination of inorganic and biologically mediated geochemical processes. Whereas the formation of scorodite relates to the oxidation of arsenopyrite, we hypothesize that the presence of orpiment and realgar is associated to scorodite dissolution and subsequent precipitation of these two minerals within the mine tailings deposit under moderately reducing conditions. The occurrence of organic debris and reduced organic sulfur compounds evidences the activity of sulfate-reducing bacteria (SRB) and provides a plausible explanation to the reactions leading to the formation of authigenic realgar and orpiment. The precipitation of these two minerals in the mine tailings, according to our hypothesis, has important consequences for As mobility since this process would reduce the release of As into the surrounding environment. Our work provides for the first time valuable hints on As speciation in a massive submarine sulfide mine tailings deposit, which is highly relevant for similar situations worldwide.

Continental margins play a key role in the cycling of natural and anthropogenic trace metals (TMs) as pathways at the interface between landmasses and deep ocean basins but also as sinks. Knowledge of how short-lived forcings alter the export dynamics of TMs is essential for our understanding of their fate in that setting. Here we report time series of particulate metal fluxes in three submarine canyons -namely Escombreras, Almeria and the Garrucha-Almanzora system- of the South-Western Mediterranean Sea. Our research focuses on combining multi-elemental TMs (Al, Fe, Ti, Co, Cu, Mn, Ni, Pb and Zn) and As (a metalloid) contents of settling particles collected near the bottom by automated particle traps during one year, and seafloor sediment samples from below the traps. We assess the role of storms and bottom trawling in the off-shelf transport of particulate TMs and As, and the natural and anthropogenic contributions of TMs by using enrichment factors (EFs).The TM export fluxes and composition changed over the study period, from March 2015 to March 2016. TM fluxes increase in early spring 2015 in association with short-lived storm events and during calm months in the Garrucha-Almanzora Canyon system, likely due to sediment resuspension triggered by bottom trawling. In terms of composition, TMs in the sinking fluxes appear to be closely associated with lithogenic (Al, Fe and Ti) and authigenic (Mn) particles' proxies. During storm events, the mass of settling particles in Escombreras and Almeria canyons was impoverished in Al, Fe, As, Co, Cu, Mn and Ni compared to other periods. The Garrucha-Almanzora Canyon system behaves differently as the above-described differences, are not observed there. Moreover, the TM composition of the sediments -with higher contents of Fe, Ti and several other TMs- in this canyon is barely tied to the composition of the settling particles. Finally, Cu and Zn contents, together with Pb in the northernmost Escombreras Canyon, are best explained by referring to anthropogenic sources. This work provides insights into the profound influence of the natural and anthropogenic forcings controlling the distributions and seasonal dynamics of particulate TMs and As in submarine canyons.

Coastal lagoons are transitional environments between continental and marine aquatic systems. Globally, coastal lagoons are of great ecological and socioeconomic importance as providers of valuable ecosystem services. However, these fragile environments are subject to several human pressures, including pollution by microplastics (MPs). The aim of this review was to identify and summarize advances in MP pollution research in coastal lagoons across the world. We consider peer-reviewed publications on this topic published in English and Spanish between 2000 and April 21, 2022, available in Scopus and Google Scholar. We found 57 publications with data on MP abundances and their characteristics in 50 coastal lagoons from around the world, 58% of which have some environmental protection status. The number of publications on this type of pollution in lagoons has increased significantly since 2019. Methodological differences amongst studies of MPs in coastal lagoons were nevertheless a limiting factor for wide-ranging comparisons. Most studies (77%) were conducted in single environmental compartments, and integration was limited, hampering current understanding of MP dynamics in such lagoons. MPs were more abundant in lagoons with highly populated shores and watersheds, which support intensive human activities. On the contrary, lagoons in natural protected areas had lower abundances of MPs, mostly in sediments and organisms. Fiber/filament and fragment shapes, and polyethylene, polyester, and polypropylene polymers were predominant. MPs had accumulated in certain areas of coastal lagoons, or had been exported to the sea, depending on the influence of seasonal weather, hydrodynamics, anthropogenic pressures, and typology of MPs. It is advised that future research on MP pollution in coastal lagoons should focus on methodological aspects, assessment/monitoring of pollution itself, MP dynamics and impacts, and prevention measures as part of a sound environmental management.

Research on plastic pollution has rapidly expanded in recent years and has led to the discovery of vast amounts of microplastics floating on the surface of subtropical oceanic gyres. However, the distribution of floating plastic in the ocean is still poorly constrained, and there is a lack of information from a few meters from the coastline where the largest plastic emissions take place. Here, we provide a comprehensive study on the loads of plastic debris in the coastal surface waters of the NW Mediterranean Sea using data from 124 manta trawl deployments collected along 7 months by citizen scientists. Our results reveal that pollution by microplastics in the nearshore is likely subject to seasonal variations associated to a combination of hydrodynamic and anthropogenic pressures. The high proportions of microplastics found indicate that potential breakdown of plastics in the nearshore may take place in line with previous works. We prove that citizen science is a powerful tool in plastic research to monitor microplastics in the nearshore as it provides scientifically meaningful results while stimulating citizen engagement. Future studies may benefit from targeting specific scientific open questions by using the citizen science methodological approach presented here.

Submarine canyons are deep, large-scale incisions that occur on the continental shelf and slope of all ocean margins. These landforms serve as preferential particle-transport conduits that connect the coastal zone with the deep-sea. Canyons have been studied for decades and are among the most iconic submarine geomorphic features. Advances in marine technology are increasingly providing new understanding of the physical and biological processes that take place in canyons, which are also notoriously affected by the impact of anthropogenic activities. In this article we describe the main geomorphic characteristics of submarine canyons and synthesize the past and current knowledge on their formation, evolution, global distribution and hydrodynamical and ecological significance.

Industrial seabed mining is expected to cause significant impacts on marine ecosystems, including physical disturbance and the generation of plumes of toxin-laden water. Portmán Bay (NW Mediterranean Sea), where an estimated amount of 60 Mt of mine tailings from sulphide ores were dumped from 1957 to 1990, is one of the most metal-polluted marine areas in Europe and worldwide. This bay can be used to assess the impact on marine ecosystems of particle settling from sediment plumes resulting from mine tailings resuspension. With this purpose in mind, we conducted a field experiment there to investigate subsequent effects of deposition of (artificially resuspended) contaminated sediments on (i) prokaryotic abundance and meiofaunal assemblages (in terms of abundance and diversity), (ii) the availability of trophic resources (in terms of organic matter biochemical composition), and (iii) a set of ecosystem functions including meiofaunal biomass, heterotrophic C production and C degradation rates. The results of this study show that mine tailings resuspension and plume deposition led to the decline of prokaryotic abundance and nematode's biodiversity. The later decreased because of species removal and transfer along with particle resuspension and plume deposition. Such changes were also associated to a decrease of the proteins content in the sediment organic matter, faster C degradation rates and higher prokaryotic C production. Overall, this study highlights that mine tailing resuspension and ensuing particle deposition can have deleterious effects on both prokaryotes and nematode diversity, alter biogeochemical cycles and accelerate C degradation rates. These results should be considered for the assessment of the potential effects of seabed mineral exploitation on marine ecosystems at large.